Atomizers for liquids pressurized by a manually operated pump basically comprise a hollow tubular support extending along a longitudinal axis and defining an internal cylindrical wall, with a first axial opening at one end for the intake of the liquid pressurized by the pump, and a second axial opening at the opposite end; a body provided with a nozzle arranged in correspondence with the second aperture and sealed tightly with the tubular support; an obturator, inside the support, for closing and opening the nozzle; a plunger member, cooperating with the cylindrical cavity in the tubular support, the plunger member being connected to the obturator for the axial movement thereof under the action of the pressure of the liquid determined by the pump; a guide sleeve for the obturator; a cavity through the sleeve and the body provided with the nozzle, the cavity facing the nozzle; a spring for urging the obturator against the nozzle and holding it closed with a predetermined resilient load; and a passageway for the liquid through the first aperture and the cavity facing the nozzle.
Atomizers having the aforementioned characteristics are well-known in the prior art, one example being illustrated in U.S. Pat. No. 2,717,178. Similar prior art structures are shown in U.S. Pat. Nos. 4,182,496 and 4,830,284. In all of the atomizers described in these documents, however, it is apparent that when the liquid to be delivered reaches a specific pressure, the obturator overcomes the resilient load of the spring and moves axially, thereby opening the nozzle. Unfortunately, with the nozzle open, the pressure exerted by the pump causes the liquid to be immediately discharged outside without any control. The pump, being manual, generates a pressure which can vary widely in the range of an operating cycle and which changes from cycle to cycle.
This disadvantage is made worse by the fact that, in the prior art devices mentioned above, delivery occurs while the cavity is upstream of the nozzle and in the process of shaping and varying its geometry as a result of the gradual withdrawal of the obturator against spring loading.
Indeed, it has been found that, particularly when manually operated pumps without pressurizers are used, if the liquid is delivered before the chamber upstream of the nozzle has adopted a specific geometry and has reached a specific minimum volume, depending on the type of liquid to be delivered, it is not possible to repeat the desired fan shape of the sprayed jet constantly.
For each actuating cycle of the pump, the liquid can, in fact, be delivered initially in the form of a compact squirt and then, when the pump pressure reaches its maximum in the actuating cycle, in the form of a fan-shaped spray, returning to a compact squirt again when the pump pressure drops to zero at the end of the operating cycle.
Accordingly, prior art atomizers suffer from a delivery problem in which the dimensions of the jet are neither constant nor uniform, with the result that there is an excessive consumption of liquid regardless of the surfaces sprayed.